Crown block



Feb. 7, 1939.

J. M. 'SHIMER CROWN BLOCK 4 Sheet-Sheet 1 Filed Aug. 10, 1955 INVENT OR.

Lbh NM 5/1/4455 ATTORNEYS Feb. 7, 1939. J. M. SHIMER 2,146,360

CROWN BLOCK Filed Aug. 10, 1935 4 Sheets-Sheet 2 INV ENT OR.

L/H/V MASH/MATE.

BYZWS QWL ATTORNEYS Feb. 7, 1939. J. M SHIMER 2,146,360

CROWN BLOCK Filed Aug. 10, 1955 4 SheetsSheet 4 $78. %:-9.

INVENTOR.

g/H/VM 15/1/4455.

FY W

ATTORNEYJ Patented Feb. 7, 1939 UNITED STATES CROWN BLOCK John M.Shimer, Dallas, Ten, assignor to Oil Well Supply Company, Dallas, Ten, acorporation of New Jersey Application August 10, 1935, Serial No. 35,677

4 Claims.

ticularly of the center pin type for oil well derricks.

A crown block is mounted on the top or water 5 table of a drillingderrick and provided with a number of sheaves over which the line ofcable for supporting the travelling block is reeved. In drilling verydeep wells by rotary drills the loads supported from the crown block arevery heavy inasmuch as they comprise the hollow stem or pipe extendingto the bottom of the well, the rotary drill and the supporting tackle.This necessitates the use of cable of large diameter and this in turnrequires large diameter sheaves 15 in order to prevent excessive bendingand wear of the cable. Where a large number of sheaves are required, anexcessive bending weight is imposed upon the pin or shaft supporting thesheaves and if an intermediate beam is used, 20 the sheaves must beseparated and thus moved out of direct alignment with the sheaves of thetravelling block, so that a considerable side wear on the sheaves andcable takes place particularly when the travelling block is at or nearthe top 2 of the derrick. Heretofore, double deck crown blocks have beenused in order to obtain a compact reeving of the line, but thisconstruction limits the diameter of certain of the sheaves and thus hasthe disadvantage of rapid wear of the cables, if large diameter cablesare employed.

In my present invention I provide a center pin type of crown block witha support midway of or between the ends of the pin while maintaining aclose spacing of the sheaves to approximate 35 alignment with thetravelling block sheaves which are spaced and with means close togetherto reduce the overall width to take up any side thrust that may becaused by a misalignment of the drilling shaft and also to permit anadvan- 40 tageous reeving of the cables for handling the drill stem orpipe. My invention also provides a crown block which can be easily andquickly mounted on the water table of the derrick.

The various features of my present invention 45 are illustrated by wayof example in the accompanying drawings in which- Fig. 1 is a sideviewand Fig. 2 a vertical section on a plane parallel to that of Fig. 1 of acrown block embodying a preferred form 5 of, the invention; Fig. 3 is avertical section through the crown block taken on line 3-3 of Myinvention relates to a crown block par- 7 of Fig. 5 of portions of thecrown block; Figs. 8 and 9 are diagrammatic showings of the reevings andtravelling block for California and Mid-Continent rigs respectively, andFigs. 10 and 11 are diagrammatic views showing the position of the crownblocks in the California and Mid-Continent derricks.

In my present invention the sheaves of a crown block are rotatablymounted on a center pin which is supported at each end on the frame 10of the crown block. The center pin is supported midway of the endsupports by a truss member suitably flanged above the sheaves to providesufficient rigidity and strength, but having a relatively narrow web inwhich the center pin 15 is mounted to avoid excessive spacing of thesheaves on opposite sides of the truss. The several sheaves are spacedby thrust plates at the hub portions to receive any side thrusts thatmay be imparted in the event of a bent grief go stem or kelly. The baseof the crown block is made of a rectangular frame which may be spreadapart to permit the center pin and its sheaves to be hoisted upwardlytherethrough whereupon it may be. closed to receive the supports of thecenter pin. A deflection sheave is mounted on the frame so that thecable line may be reeved in such a manner that the travelling block maybe guided by the derrick man with the slowest moving parts of the cablewhich connect the crown block and travelling block nearest to him whenin his regular position in the derrick for handling pipe.

Referring more particularly to the accompanying drawings, severalsheaves I5, six being shown by way of example, are rotatably mounted ona center pin l6 which is supported at each end in bearings I! that restupon the frame l8 of the crown block. The sheaves l5 are individuallymounted on rollerbearings l9 which are supplied with lubricant throughindividual passages 20 in the center pin.

The center pin I6 is also supported midway of the bearings I! by a truss2|, the ends of which rest on the frame H! as shown at 22 in Figs. 1 and2. The truss 2| comprises a vertical web 23 reinforced by ribs 24 and isprovided at its upper edge with flanges 25 that overlie the edges of thesheaves. The web 23 and reinforcing ribs 24 have much less thickness orwidth than the flanges 25 and therefore permit a closer spacing of thesheaves than would be the case if an intermediate beam were employed, inwhich case the sheaves would be separated the full width of the flanges25.

The individual sheaves II are separated from theendbearingsllandfromthetrussli and from each other by thrust plates 2' positionedbetween the hubs of the sheaves so as to takeupsidethrustsandweartbatmayresuitifthe travelling block is thrown out ofalignment with the crown blockby a bending of the grief stem or byother-causes. In this way an excessive wearing of the sheaves isavoided.

The supporting bearings l1 and the truss 2| are removably bolted on theframe it so that the center pin and its supports may be disassembledfrom the frame I. and placed separately to the top of the derrick andinstalled. This is of great advantage because the total weight of thecrown block is very great. In hoisting and assembling the crown block,therefore, the bearings i1 and the truss 2i are removedfrom the frameand the latter hoisted above and placed on the water table of thederrick and the center pin, sheaves and supports are then hoisted as aunit and set in position on the frame.

The frame ll comprises a pair of longitudinally extending spaced beams21 and a pair of connecting cros beams I. bolted to the webs of theieams 2! by means of angle plates 29 and bolts fill. After the frame llhas been placed on the water table, the bolts 30 at one end may beremoved and the side beam 21 spread sufficiently to permit the centerpin and its sheaves and supports to be hoisted upwardly through theopening. Thereupon the side beam 21 may be joined to the end beams IIand the center pin and its sheaves lowered until the bases of thebearings I1 and the truss 2! rest in'their proper position on the frameand are bolted thereto by means of bolts 3i.

After the crown block has been installed on the top of the derrick or onthe water table, a cable line 32 may be reeved about the sheaves 15 ofthe crown block and sheaves ll of a travelling block as shown in Figs. 8and 9. In the California type of rig, shown in Figs. 8 and 10, one end aof the cable line is passed around a defleeting pulley 35 and thensecured to a calf wheel I at the base of the derrick. This is known asthe dead end of the line. The other end 31 extends downwardly to thehoist 38. This is known as the live end of the line. In theMid-Continent type of r ging as shown in Fig. 9, the fixed or dead end34 may be secured to the derrick and the travelling or live end 31 issecured to the hoist II as in the California type of rigging. With theCalifornia type of rig it will be apparent that those lengths of thecable line nearest the left of Fig. 8 and, therefore, nearest the movingend 31, travel at a greater speed than those to the right, where thesupporting strands are nearest the fixed end of the line.

This is of advantage in the California type of rig, particularly,becausethe window of the derrick is at the left in a position shown in Fig. 10,as indicated at 3!, and the lengths of the pipe or hollow drill stem areracked against the opposite side of the derrick as at 4|, that is, atthe right in Hg. 10, and the derrick man in guiding the travelling block31 may do so by grasping the nearest parts of the cable line which arethe slower moving lines. This is much easier and less dangerous than ifthe linesat'this side of the derrick were the faster travelling lines.

Itwlllbenotedthatthereisaminimumof deflection of the lines between thecrown block andthetnvellingblochbecauseofthetruss 2|andthereforeaminimnmdeflection of the-cable even when the travellingblock approaches the crown block. Consequently there is a. minimum ofside wear of the line against the grooved edges of the sheaves. Theedges of the sheaves may be very closely spaced, but a fraction of aninch, so there is no danger of the cable falling between the sheaves anda very compact arrangement is obtained.

The deflecting pulley 35 may be mounted in a bracket ii at one of thelongitudinal beams 21. Similarly a cat line sheave I! may be mounted ona bracket 43 secured by clamps 44 to a lower flange of one of the beams21 as shown in Figs. 5 and 6.

A sand line sheave ll may also be mounted on a bracket 45 on one of thecross beams 28, as shown in Figs. 5 and 7, when the crown block is usedin a Mid-Continent rig as shown in Figs. 9 and 11. When the crown blockis to be used for a California type rig, the sand line sheave 46 may bemounted in a bracket ll secured to a web of one of the beams 21, so asto align with the window of the derrick,

By the above invention, therefore. I have provided a multiple sheaveheavy duty crown block having a center pin that is supportedintermediate its ends without an intermediate beam that would cause awide spacing of the sheaves on opposite sides of the beam and thus adisplacement from alignment with the sheaves of the crown block.Excessive wear on the grooves of the sheaves and on the cable is thusavoided. Excessive wear between the sheaves is avoided by the use of thethrust plates which take up any i such thrust that may be caused in theevent that the grief stem should throw the travelling block out ofalignment. The invention also provides a very compact crown block that.may be readily mounted on the derrick and which permits the reeving ofthe cable so as to place the most slowly travelling lengths nearest thederrick man for guiding the travelling block.

The weight and stresses on the crown block are distributed equally atthe bearings for the center pin and at the ends of the truss therefor,distributing the stresses equally at four points spaced at angles of 90from each other. This will be apparent because the center pin beinguniformly loaded, one-half of the load will be taken. by the truss atthe center of the center pin and distributed equally at the two ends ofthe truss, and the remaining one-half will be. equally distributed tothe two bearings of the center pin.

What I claim is:

1. A multiple sheave crown block having a f center pin, sheaves mountedon said pin, a supporting frame having a pair of spaced bearings, one ateach end of said pin, a truss between said bearings supported on saidframe and supporting said center pin intermediate said bearings, saidtruss extending above said sheaves and having a flange extending partlyover said sheaves.

2. A multiple sheave crown block having a center pin, sheaves mounted onsaid pin, a supporting frame having a pair of spaced bearings, one ateach end of said pin, a truss between said bearings supported on saidframe and supporting said center pin intermediate said bearings, saidtruss having a relatively thin web and ribs between said sheaves and awider flange above the sheaves.

3. A multiple sheave crown block having a center pin, sheaves mounted onsaid pin, a supporting frame having a pair of side membersmoimtedsothattheymaybespreadapartto permit the passage between them ofsaid pin and sheaves and replaced, a pair of bearings, one at each endof said pin, to be supported on said members, a truss between saidbearings supported on said members and supporting said center pinintermediate said bearings, said truss extending above said sheaves andhaving a flange above and overlapping said sheave.

- 4. A multiple sheave crown block comprising a frame consisting of sideand cross pieces joined together to Iform an integral supportingstructure,

a sheave pin, means providing bearing supports for the ends of saidsheave pin on the top of said side pieces midway between said crosspieces, means providing a center support for said pin on top of saidcross pieces midway between said side pieces, a plurality of sheaves onsaid pin equally divided on opposite sides of said central support, anda plurality of spacer elements separating said sheaves from each otherand from said bearing and center support means.

' JOHN M. SHIMER.

